This invention relates generally to image reconstruction, and more particularly, to methods and systems for reconstruction of volumetric computed topography (CT) images.
Three-dimensional (3D) or cone beam (CB) filtered backprojection (FBP) is used in multi-row CT scanners to provide volumetric CT (VCT) scanning operation. It is known to use 3D backprojection algorithms in VCT scanners to reconstruct images using a mapping process. For example, 3D FBP may be used for image reconstruction from cone beam projections acquired from a circular source trajectory. Using a pixel based backprojection, a mapping process is typically performed from the center of a reconstructed pixel to a detector plane. However, in many instances it is unlikely that the reconstruction point is at the center of a detector row. As a result, interpolation is performed across rows of the detector. For example, a back-projected value is determined, which is the weighted sum of several filtered projection samples (e.g., four filtered projection samples from four adjacent detector elements).
Thus, known backprojection processes performing interpolation use several detector elements, which may be from adjacent rows of the detector, to calculate a back-projected value from an intersecting location. An estimated value is thereby used for reconstructing images. This process results in a larger reconstructed image slice thickness, thereby reducing spatial resolution.